1. Field of the Invention
The present invention relates to an information recording device by means of which an information signal such as a picture signal, sound signal and the like are recorded on a recording medium and new information is added to the recording medium on which the initial information has been recorded.
2. Brief Description of the Prior Art
In the present specification, the video tape recorder (VTR) making use of magnetic tape and a magnetic head is used as an example.
In the conventional type VTR using a cassette and a magnetic head, the picture signal is recorded on an inclined track by means of a rotary head, while the control signal and the sound signal are recorded on the two straight tracks at both ends of the magnetic tape. An example of such a helical scanning type cassette VTR is shown in FIG. 1.
In the drawing, the tape has been loaded in the VTR. The apparatus includes a cassette 1, a magnetic tape 2, and rotary magnetic heads 3 and 4 arranged on a rotary head drum. The capstan 9 and the pinch roller 8, feed the tape 2 in the direction of the arrow 10 at a constant speed. In this way, the magnetic tape 2 runs along the circumference of the head drum, whereby along with the rotation of the rotary heads 3 and 4 in the direction of the arrow 11 the inclined track is formed on the magnetic tape 2. The erasing head 5 is provided for erasing the total width of the tape 2, the erasing head 6 is only for erasing the sound track and the recording reproducing head cooperates only with the sound track and the control signal track.
FIG. 2 shows an example of the pattern on the magnetic tape on which the information is recorded by means of the VTR in FIG. 1. There is shown in the drawing, a track 12 for recording the control signal, a track 13 for recording the sound signal and a video track 14 on which the picture signal is recorded by means of the two rotary magnetic heads 3 and 4, whereby the 1-line 1-field video signal is recorded in accordance with a conventional azimuth recording system. Furthermore, the sound signal is recorded by means of the fixed head 7 on the sound track, at a first lateral extremity of the tape, while at the same time, the CTL signal for obtaining the synchronization at the time of reproduction is recorded on the control track 12 at the other lateral extremity.
In the above described conventional system in order to carry out sound post recording, the sound signal recorded on the sound track 13 is erased by means of the erasing head 6, which cooperates exclusively with the sound track, and a new sound signal is recorded by means of the fixed head 7.
On the other hand, in order to lower the quantity of magnetic tape required, to have a compact and light cassette and cooperating apparatus, the width of the recording trace is narrowed and the running speed of the magnetic tape is decreased and the recording density of the picture signal is increased. However, when the running speed of the magnetic tape is decreased substantially, it is difficult to maintain frequency characteristics sufficient for a fixed head sound signal. Under such circumstances a system is considered in which the signal composed of the picture signal and the sound signal is recorded and reproduced by means of the same rotating magnetic head. However, in accordance with this system, the picture signal and the sound signal are recorded composed, so that post recording of the sound signal is impossible.